model.cc

   1 #include <stdio.h>
   2
   3 #include "model.h"
   4 #include "action.h"
   5 #include "tree.h"
   6 #include "schedule.h"
   7 #include "common.h"
   8
   9 #define INITIAL_THREAD_ID       0
  10
  11 class Backtrack {
  12 public:
  13         Backtrack(ModelAction *d, action_list_t *t) {
  14                 diverge = d;
  15                 actionTrace = t;
  16                 iter = actionTrace->begin();
  17         }
  18         ModelAction * get_diverge() { return diverge; }
  19         action_list_t * get_trace() { return actionTrace; }
  20         void advance_state() { iter++; }
  21         ModelAction * get_state() {
  22                 return iter == actionTrace->end() ? NULL : *iter;
  23         }
  24 private:
  25         ModelAction *diverge;
  26         action_list_t *actionTrace;
  27         /* points to position in actionTrace as we replay */
  28         action_list_t::iterator iter;
  29 };
  30
  31 ModelChecker *model;
  32
  33 ModelChecker::ModelChecker()
  34 {
  35         /* First thread created will have id INITIAL_THREAD_ID */
  36         this->next_thread_id = INITIAL_THREAD_ID;
  37         used_sequence_numbers = 0;
  38         /* Initialize default scheduler */
  39         this->scheduler = new Scheduler();
  40
  41         num_executions = 0;
  42         this->current_action = NULL;
  43         this->exploring = NULL;
  44         this->nextThread = THREAD_ID_T_NONE;
  45
  46         rootNode = new TreeNode();
  47         currentNode = rootNode;
  48         action_trace = new action_list_t();
  49 }
  50
  51 ModelChecker::~ModelChecker()
  52 {
  53         delete action_trace;
  54         delete this->scheduler;
  55         delete rootNode;
  56 }
  57
  58 void ModelChecker::reset_to_initial_state()
  59 {
  60         DEBUG("+++ Resetting to initial state +++\n");
  61         std::map<int, class Thread *>::iterator it;
  62         for (it = thread_map.begin(); it != thread_map.end(); it++)
  63                 delete (*it).second;
  64         thread_map.clear();
  65         action_trace = new action_list_t();
  66         currentNode = rootNode;
  67         current_action = NULL;
  68         next_thread_id = INITIAL_THREAD_ID;
  69         used_sequence_numbers = 0;
  70         /* scheduler reset ? */
  71 }
  72
  73 thread_id_t ModelChecker::get_next_id()
  74 {
  75         return next_thread_id++;
  76 }
  77
  78 int ModelChecker::get_next_seq_num()
  79 {
  80         return ++used_sequence_numbers;
  81 }
  82
  83 Thread * ModelChecker::schedule_next_thread()
  84 {
  85         Thread *t;
  86         if (nextThread == THREAD_ID_T_NONE)
  87                 return NULL;
  88         t = thread_map[id_to_int(nextThread)];
  89
  90         ASSERT(t != NULL);
  91
  92         return t;
  93 }
  94
  95 /*
  96  * get_next_replay_thread() - Choose the next thread in the replay sequence
  97  *
  98  * If we've reached the 'diverge' point, then we pick a thread from the
  99  *   backtracking set.
 100  * Otherwise, we simply return the next thread in the sequence.
 101  */
 102 thread_id_t ModelChecker::get_next_replay_thread()
 103 {
 104         ModelAction *next;
 105         thread_id_t tid;
 106
 107         next = exploring->get_state();
 108
 109         if (next == exploring->get_diverge()) {
 110                 TreeNode *node = next->get_node();
 111
 112                 /* Reached divergence point; discard our current 'exploring' */
 113                 DEBUG("*** Discard 'Backtrack' object ***\n");
 114                 tid = node->getNextBacktrack();
 115                 delete exploring;
 116                 exploring = NULL;
 117         } else {
 118                 tid = next->get_tid();
 119         }
 120         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
 121         return tid;
 122 }
 123
 124 thread_id_t ModelChecker::advance_backtracking_state()
 125 {
 126         /* Have we completed exploring the preselected path? */
 127         if (exploring == NULL)
 128                 return THREAD_ID_T_NONE;
 129
 130         /* Else, we are trying to replay an execution */
 131         exploring->advance_state();
 132
 133         ASSERT(exploring->get_state() != NULL);
 134
 135         return get_next_replay_thread();
 136 }
 137
 138 bool ModelChecker::next_execution()
 139 {
 140         DBG();
 141
 142         num_executions++;
 143         print_summary();
 144         if ((exploring = model->get_next_backtrack()) == NULL)
 145                 return false;
 146
 147         if (DBG_ENABLED()) {
 148                 printf("Next execution will diverge at:\n");
 149                 exploring->get_diverge()->print();
 150                 print_list(exploring->get_trace());
 151         }
 152
 153         model->reset_to_initial_state();
 154         nextThread = get_next_replay_thread();
 155         return true;
 156 }
 157
 158 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 159 {
 160         action_type type = act->get_type();
 161
 162         switch (type) {
 163                 case THREAD_CREATE:
 164                 case THREAD_YIELD:
 165                 case THREAD_JOIN:
 166                         return NULL;
 167                 case ATOMIC_READ:
 168                 case ATOMIC_WRITE:
 169                 default:
 170                         break;
 171         }
 172         /* linear search: from most recent to oldest */
 173         action_list_t::reverse_iterator rit;
 174         for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
 175                 ModelAction *prev = *rit;
 176                 if (act->is_dependent(prev))
 177                         return prev;
 178         }
 179         return NULL;
 180 }
 181
 182 void ModelChecker::set_backtracking(ModelAction *act)
 183 {
 184         ModelAction *prev;
 185         TreeNode *node;
 186         Thread *t = get_thread(act->get_tid());
 187
 188         prev = get_last_conflict(act);
 189         if (prev == NULL)
 190                 return;
 191
 192         node = prev->get_node();
 193
 194         while (t && !node->is_enabled(t))
 195                 t = t->get_parent();
 196
 197         /* Check if this has been explored already */
 198         if (node->hasBeenExplored(t->get_id()))
 199                 return;
 200         /* If this is a new backtracking point, mark the tree */
 201         if (node->setBacktrack(t->get_id()) != 0)
 202                 return;
 203
 204         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 205                         prev->get_tid(), t->get_id());
 206         if (DBG_ENABLED()) {
 207                 prev->print();
 208                 act->print();
 209         }
 210
 211         Backtrack *back = new Backtrack(prev, action_trace);
 212         backtrack_list.push_back(back);
 213 }
 214
 215 Backtrack * ModelChecker::get_next_backtrack()
 216 {
 217         Backtrack *next;
 218         if (backtrack_list.empty())
 219                 return NULL;
 220         next = backtrack_list.back();
 221         backtrack_list.pop_back();
 222         return next;
 223 }
 224
 225 void ModelChecker::check_current_action(void)
 226 {
 227         ModelAction *next = this->current_action;
 228
 229         if (!next) {
 230                 DEBUG("trying to push NULL action...\n");
 231                 return;
 232         }
 233         current_action = NULL;
 234         nextThread = advance_backtracking_state();
 235         next->set_node(currentNode);
 236         set_backtracking(next);
 237         currentNode = currentNode->explore_child(next);
 238         this->action_trace->push_back(next);
 239 }
 240
 241 void ModelChecker::print_summary(void)
 242 {
 243         printf("\n");
 244         printf("Number of executions: %d\n", num_executions);
 245         printf("Total nodes created: %d\n", TreeNode::getTotalNodes());
 246
 247         scheduler->print();
 248
 249         print_list(action_trace);
 250         printf("\n");
 251
 252 }
 253
 254 void ModelChecker::print_list(action_list_t *list)
 255 {
 256         action_list_t::iterator it;
 257
 258         printf("---------------------------------------------------------------------\n");
 259         printf("Trace:\n");
 260
 261         for (it = list->begin(); it != list->end(); it++) {
 262                 (*it)->print();
 263         }
 264         printf("---------------------------------------------------------------------\n");
 265 }
 266
 267 int ModelChecker::add_thread(Thread *t)
 268 {
 269         thread_map[id_to_int(t->get_id())] = t;
 270         scheduler->add_thread(t);
 271         return 0;
 272 }
 273
 274 void ModelChecker::remove_thread(Thread *t)
 275 {
 276         scheduler->remove_thread(t);
 277 }
 278
 279 int ModelChecker::switch_to_master(ModelAction *act)
 280 {
 281         Thread *old;
 282
 283         DBG();
 284         old = thread_current();
 285         set_current_action(act);
 286         old->set_state(THREAD_READY);
 287         return Thread::swap(old, get_system_context());
 288 }
 289
 290 ModelAction::ModelAction(action_type_t type, memory_order order, void *loc, int value)
 291 {
 292         Thread *t = thread_current();
 293         ModelAction *act = this;
 294
 295         act->type = type;
 296         act->order = order;
 297         act->location = loc;
 298         act->tid = t->get_id();
 299         act->value = value;
 300         act->seq_number = model->get_next_seq_num();
 301 }
 302
 303 bool ModelAction::is_read()
 304 {
 305         return type == ATOMIC_READ;
 306 }
 307
 308 bool ModelAction::is_write()
 309 {
 310         return type == ATOMIC_WRITE;
 311 }
 312
 313 bool ModelAction::is_acquire()
 314 {
 315         switch (order) {
 316         case memory_order_acquire:
 317         case memory_order_acq_rel:
 318         case memory_order_seq_cst:
 319                 return true;
 320         default:
 321                 return false;
 322         }
 323 }
 324
 325 bool ModelAction::is_release()
 326 {
 327         switch (order) {
 328         case memory_order_release:
 329         case memory_order_acq_rel:
 330         case memory_order_seq_cst:
 331                 return true;
 332         default:
 333                 return false;
 334         }
 335 }
 336
 337 bool ModelAction::same_var(ModelAction *act)
 338 {
 339         return location == act->location;
 340 }
 341
 342 bool ModelAction::same_thread(ModelAction *act)
 343 {
 344         return tid == act->tid;
 345 }
 346
 347 bool ModelAction::is_dependent(ModelAction *act)
 348 {
 349         if (!is_read() && !is_write())
 350                 return false;
 351         if (!act->is_read() && !act->is_write())
 352                 return false;
 353         if (same_var(act) && !same_thread(act) &&
 354                         (is_write() || act->is_write()))
 355                 return true;
 356         return false;
 357 }
 358
 359 void ModelAction::print(void)
 360 {
 361         const char *type_str;
 362         switch (this->type) {
 363         case THREAD_CREATE:
 364                 type_str = "thread create";
 365                 break;
 366         case THREAD_YIELD:
 367                 type_str = "thread yield";
 368                 break;
 369         case THREAD_JOIN:
 370                 type_str = "thread join";
 371                 break;
 372         case ATOMIC_READ:
 373                 type_str = "atomic read";
 374                 break;
 375         case ATOMIC_WRITE:
 376                 type_str = "atomic write";
 377                 break;
 378         default:
 379                 type_str = "unknown type";
 380         }
 381
 382         printf("(%4d) Thread: %d\tAction: %s\tMO: %d\tLoc: %14p\tValue: %d\n",
 383                         seq_number, id_to_int(tid), type_str, order, location, value);
 384 }